In the printing field, the impact type printer has been the predominant apparatus for providing increased thruput of printed information. The impact printers have included the dot matrix type wherein individual print wires are driven from a home position to a printing position by individual and separate drivers, and the full character type wherein individual type elements are caused to be driven against a ribbon and paper or like record media adjacent and in contact with a platen.
The typical and well-known arrangement in a printing operation provides for transfer of a portion of the ink from the ribbon to result in a mark or image on the paper. Another arrangement includes the use of carbonless paper wherein the impact from a print wire or a type element causes rupture of encapsulated material for marking the paper. Also known are printing inks which contain magnetic particles wherein certain of the particles are transferred to the record media for encoding characters in manner and fashion so as to be machine-readable in a subsequent operation. One of the known encoding systems is MICR (magnetic ink character recognition) utilizing the manner of operation as just mentioned.
While the impact printing method has dominated the industry, one disadvantage of this type printing is the noise level which is attained during printing operation. Many efforts have been made to reduce the high noise levels by use of sound absorbing or cushioning materials or by isolating the printing apparatus. More recently, the advent of thermal printing which effectively and significantly reduces the noise levels has brought about the requirement for heating of extremely precise areas of the record media by use of relatively high currents. The intense heating of the localized areas causes transfer of ink from a ribbon onto the paper or alternatively, the paper may be of the thermal type which includes materials which are responsive to the generated heat.
Further, it is seen that the use of thermal printing is adaptable for MICR encoding of documents wherein magnetic particles are caused to be transferred onto the documents for machine reading of the characters. The thermal transfer printing approach for use in MICR encoding of documents enables reliability in operation at the lower noise levels.
Representative documentation in the area of transfer material formulations and transfer mediums for use in non-impact printing includes U.S. Pat. No. 3,519,464, issued to L. A. Balster et al. on July 7, 1970, which discloses a heat sensitive element comprising a support paper with a heat sensitive layer of thermoplastic composition and including N-ethyl-p-toluene sulfonamide as a plasticizer for said composition of an organic acid ester, a vinyl acetate polymer, a tackifier, an organic dye, carbon black, and an alkali metal silicate.
U.S. Pat. No. 3,663,278, issued to J. H. Blose et al. on May 16, 1972, discloses a thermal transfer medium having a base with a transferable coating composition of a cellulosic polymer, a thermoplastic resin, a plasticizer, and a sensible dye material.
U.S. Pat. No. 3,983,279, issued to H. Matsushita et al. on Sept. 28, 1976, discloses a multiple heat-sensitive copying medium having a color forming layer, a thermally conductive substrate, and a heat sensitive transfer layer comprising an acid and a phenol, a binder, a solvent and dioctyl phthalate (D.O.P.) plasticizer.
U.S. Pat. No. 4,251,276, issued to W. I. Ferree et al. on Feb. 17, 1981, discloses a transfer ribbon having a substrate coated with a thermally-activated ink composition comprising a thermally-stable polymer, an oil-gelling agent, and an oil dissolving medium or plasticizer such as dipropylene glycol dibenzoate present in a percentage by weight of the total nonvolatile components.
U.S. Pat. No. 4,419,024, issued to P. A. Bowlds et al. on Dec. 6, 1983, discloses a thermal transfer medium which comprises a mixed resistive layer of a thermosetting polyimide, a thermoplastic polyimide, and graphite. The ink formula includes sucrose acetate isobutyrate ethyl cellulose, carbon black, and stearic acid.
And, U.S. Pat. No. 4,421,429, issued to A. E. Graham on Dec. 20, 1983, discloses a thermal transfer medium which comprises a silicon dioxide intermediate layer. The ink formula includes sucrose acetate isobutyrate.